/* -------------------------------------------------------------------------
 *
 * pg_shmem.h
 *	  Platform-independent API for shared memory support.
 *
 * Every port is expected to support shared memory with approximately
 * SysV-ish semantics; in particular, a memory block is not anonymous
 * but has an ID, and we must be able to tell whether there are any
 * remaining processes attached to a block of a specified ID.
 *
 * To simplify life for the SysV implementation, the ID is assumed to
 * consist of two unsigned long values (these are key and ID in SysV
 * terms).	Other platforms may ignore the second value if they need
 * only one ID number.
 *
 *
 * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/storage/pg_shmem.h
 *
 * -------------------------------------------------------------------------
 */
#ifndef PG_SHMEM_H
#define PG_SHMEM_H

typedef struct PGShmemHeader /* standard header for all Postgres shmem */ {
    int32 magic; /* magic # to identify openGauss segments */
#define PGShmemMagic 679834894
    ThreadId creatorPID; /* PID of creating process */
    Size totalsize;      /* total size of segment */
    Size freeoffset;     /* offset to first free space */
    void* index;         /* pointer to ShmemIndex table */
#ifndef WIN32            /* Windows doesn't have useful inode#s */
    dev_t device;        /* device data directory is on */
    ino_t inode;         /* inode number of data directory */
#endif
} PGShmemHeader;

#ifdef EXEC_BACKEND
#ifndef WIN32
extern THR_LOCAL unsigned long UsedShmemSegID;
#else
extern THR_LOCAL HANDLE UsedShmemSegID;
#endif
extern THR_LOCAL void* UsedShmemSegAddr;

extern void PGSharedMemoryReAttach(void);
#endif

extern THR_LOCAL void* UsedShmemSegAddr;

#define PGSharedMemoryAttached() (NULL != UsedShmemSegAddr)

extern PGShmemHeader* PGSharedMemoryCreate(Size size, bool makePrivate, int port);
extern bool PGSharedMemoryIsInUse(unsigned long id1, unsigned long id2);
extern void PGSharedMemoryDetach(void);
extern void cancelIpcMemoryDetach(void);

#endif /* PG_SHMEM_H */
